The "Mystery'" sonatas for scordato violin and continuo by H. I. F. Biber (1644-1704) had been largely ignored until 1905, when they were included in the collection of Austrian masterpieces, Denkmäler der Tonkunst der 0sterreich. Even then, they were the cause of some confusion which was later corrected in an addenda to the volume which included this series of sonatas. In the baroque period, scordatura was used by a few of Biber's contemporaries, but the technique is not commonly used today. In order to fully understand and to appreciate the " mystery" sonatas, a knowledge of scordatura is necessary, and this technique is discussed in Chapter II. Because the 17th century violins differed slightly from those used today, and the resources of the instrument had not yet been fully developed, a discussion of these aspects has been included. A comparison of the works of Biber with those of his contemporaries shows him to be an innovator who contributed greatly to the growing technique of the violin.